Oxidation-resistant composite reverse osmosis membrane

a reverse osmosis membrane and composite technology, applied in the field of reverse osmosis membranes, can solve the problems of reducing the water flux of the membrane, reducing the salt rejection of the membrane, and contaminating the polyamide ro membrane, so as to improve the performance of the reverse osmosis membrane, improve the resistance to oxidation and organic fouling, and prolong the li

Inactive Publication Date: 2008-08-28
VONTRON MEMBRANE TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0044]According to a still further aspect of the invention, there is provided a process for improving performances of a reverse osmosis membrane comprising a polyamide layer, which comprises modifying the polyamide layer with a persulfate.
[0045]In comparison with conventional RO membranes in the art, the RO membrane of the invention has improved resistance to oxidation and organic fouling, and a longer life-span under working conditions. Furthermore, the RO membrane of the invention has relatively higher salt rejection and water flux, can be easily prepared and employed, and can be washed at relatively longer intervals. The RO membrane of the invention is suitable for use in water treatment as well as other fields involving reverse osmosis.

Problems solved by technology

However, current polyamide RO membranes have a defect that they will be contaminated by organic or inorganic substances presented in water after being used in water treatment for a short period of time.
For example, contaminants presented in the raw water such as inorganic ions, bacterium, viruses, organic and colloidal substances will be adsorbed onto the membrane, thereby forming colloidal fouling and / or biofouling on the membrane, which will greatly reduce the water flux of the membrane.
Moreover, current RO membranes are very sensitive to oxidizing substances, which will greatly deteriorate the performances of the membrane at a relatively low concentration and cause a rapid decrease of the salt rejection of the membrane.
As most water resources are contaminated, some of which may be pre-treated waste water, the raw water to be treated using a RO membrane always comprises a large amount of oxidizing bactericides.
Consequently, current RO membranes used in the treatment of such raw water usually have a short life-span, and need to be replaced frequently, which will increase the cost of the treatment while decreasing the efficiency of the membranes.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples 1-2

[0072]Composite RO membranes as prepared in Comparative Example 1 were immersed in a 1% aqueous solution of potassium persulfate maintained at pH 8 by a potassium phosphate buffer for different times as shown in the following Table 1, and then dried in an oven at a temperature of 140° C. for 5 minutes to give composite RO membranes of the invention. The performances of the RO membranes were determined as described in the Comparative Example 1, and the results were shown in Table 1.

TABLE 1Performances of RO MembranesComparativeItemsExample 1Example 1Example 2Time for treatment with—1030potassium persulfate (min)Initial salt rejection (%)99.399.399.2Initial water flux (GFD)24.822.423.3After treatment with NaClOSalt rejection (%)5.886.998.8Water flux (GFD)56243.228.7

[0073]It can be found from the data as shown in Table 1 that the oxidation resistance of the RO membranes was significantly improved by the treatment with potassium persulfate.

examples 3-8

[0074]The porous support was immersed in a 2.5% solution of m-phenylenediamine (MPDA) containing 0.1 wt % of sodium dodecylbenzene sulfonate (SDBS) for about 1 min. The support was then drained and nip rolled to remove the excess aqueous solution. After that, the treated support was contacted with a 0.1% (wt / v %) solution of acid chloride in ethylhexane as shown in the following Table 2 for 50 seconds, and then dried in an oven at a temperature of 40° C. for 10 minutes to give a polyamide reverse osmosis membrane. The performances of the membrane were determined as described in Comparative Example 1, and the results were shown in Table 2.

TABLE 2Performances of RO Membranes as Prepared in Examples 3-8ItemsEx. 3Ex. 4Ex. 5Ex. 6Ex. 7Ex. 8Total concentration of acid0.10.10.10.10.10.1chlorideRelative concentration of08070504030TMC in the acid chloride (%)Relative concentration of 5-1002030506070iodo-isophthaloyl chloride (%)Initial salt rejection (%)98.999.199.399.399.299.1Initial water f...

example 9

[0076]An RO membrane was prepared according to the process as described in Example 6, except that the 5-iodo-isophthaloyl chloride was replaced by 2-iodo-terephthaloyl chloride. The performances of the membrane were determined as described in Comparative Example 1, and the results were shown in the following Table 3.

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Abstract

Disclosed is a oxidation resistant composite reverse osmosis membrane, comprising a porous support and a polyamide layer, in which the polyamide layer is modified by an agent so that the membrane retains a salt rejection of at least 85% after being subjected to an aqueous solution of NaClO having a concentration of about 2,000 to 30,000 ppm for about one hour. A process of preparing the membrane is also disclosed.

Description

CROSS-REFERENCE OF RELATED APPLICATIONS[0001]The present application claims the benefits of Chinese application No. 200610051200.5, filed on Aug. 25, 2006, entitled “an oxidation-resistant composite reverse osmosis membrane,” which is explicitly incorporated herein by reference in its entirety.TECHNICAL BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]The present invention relates to a reverse osmosis membrane, and more particularly relates to a novel composite reverse osmosis membrane comprising a modified polyamide layer, and processes for preparing the same.[0004]2. Description of Related Art[0005]Reverse osmosis technique is used for separating dissolved substances from a solution by a semi-permeable membrane having selective permeability to specified molecules, i.e. a reverse osmosis membrane (RO membrane), under a pressure in excess of the osmotic pressure of the solution. Therefore, reverse osmosis has been widely used in the purification and concentration of liquids,...

Claims

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Application Information

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IPC IPC(8): B01D39/16B05D5/00
CPCB01D67/0093B01D69/02B01D2325/30B01D71/56B01D2325/28B01D69/125
InventorZHAO, XIAOYANGHE, YAOHUAWU, ZONGCECAI, ZHIQIWANG, SILIANGLONG, CHANGYULIU, FENG
OwnerVONTRON MEMBRANE TECH CO LTD